Really Low Ph

[Bath Tussue]

I have notice that for the past few days, the PH went from 6.6 (same as tap water) to 6.0, or even off teh scale.
I have been doing 25~35% water change daily
test done with API test kit

the only thing i have changed resently is how i change the water.
before, i drain a bucketful of water, and then fill up the same amount.
now, i drain the water directly into the drain, and add water from the tap directly into the tank (after adding water conditioner into the tank)

there are also some algae on the back of the tank that i purposely didn't scape off, if it makes any difference.

what can cause the PH drop to that level??

 

[ShoC]

Firstly I would say get a bucket of water and sit it for 1 week then test it to see if It's dropped.
next guess would be any bogwood in your tank. Even though thats still a fast drop..
are you injecting co2 by any chance?

 

[Bath Tussue]

i have been doing water change every day or every 2 days, so i am assuming it is not "old" water

no wood
decorations are: real gravel (for aquarium use), and two live plant

no CO2
only a HOB aquaclear 30 filter (20 gal tank).


oh, and i have been adding a small amount of plant fertalizer for the past week.
maybe it is that?

 

[ShoC]

Sorry I'm not to sure other than that

bumping it :

 

[Daveyg1969]

Coral gravel is good at raising P.H as it adds buffers to the water that stop the P.H going all over the place.
Put some in a mesh bag and add it to your filter if there is room and remove when your P.H reaches around 7.0 or higher if you need it higher.
I use coral gravel in an emergency situation with P.H and also Nitrite, as coral gravel that has been in a tank is rich in nitrifying bacteria and can be 're-energised' at a later date by rinsing with cold water.
I must admit that when I do a water change it does make my P.H go a little haywire also, that is why I don't change as often as most people do, but my fish thank me for it

 

[Bath Tussue]

it just came back up today.
it is at 6.4 now. (tap is 6.6)

on the other hand, one of the plants is getting brown...

 

[Amunet]

I didn't have luck using coral in my tanks, so I use baking soda to raise the pH.
I add in a little every water change (once a week) and everything is great.